1. Field of the Invention
The present invention relates to a high speed quilting machine and, more particularly, to a quilting machine which is quieter and faster and operates with less downtime and for a longer period of time than quilting machines known heretofore.
2. Description of the Prior Art
Quilting machines of the general type including a bed plate, material supporting means including material feeding means for conducting material to be quilted over the bed plate, sewing thread supply means, a plurality of vertically reciprocal needles mounted on a needle support bar positioned above the bed plate for moving a plurality of threads through the material and the bed plate, vertically reciprocal presser means positioned above the bed plate for holding the material on the bed plate during formation of the stitches and for holding the material during removal of the needles therefrom, thread take-up means positioned between the thread supply means and the needles for controlling the tension in the threads during the formation of the stitches, and pattern controlling means for moving the material supporting means laterally in a preselected relationship with the material feeding means for obtaining sewing patterns, are generally old and well known in the art. An early quilting machine of this type is shown in U.S. Pat. No. 260,994, issued July 11, 1882, to William Koch. Since that time, such machines have become substantially more complex and a quilting machine of the type generally available today is shown in U.S. Pat. No. 3,385,246, issued May 28, 1968, to Kurt Schlegel.
Such machines stitch together an assembly of quilting fabrics and a filler in a pattern of stitches distributed throughout the area of the assembly. In the quilting operation, the fabrics are drawn from supply rolls while the filler is drawn from a supply roll between the fabrics to form an assembly of filler sandwiched between an upper and lower fabric. The assembly is then passed through the stitching mechanism by means of drawing rollers.
The stitching mechanism is a stationary unit and the bed plate has a plurality of holes therein, spaced transversely of the direction of movement of the material assembly, through which the needles may pass downwardly to shuttles or bobbins mounted beneath the bed plate, one for each hole and needle. Stitches are made by a downward movement of the needles through the material assembly and into and through the holes in the bed plate. Upon upward movement of the needles, loops are formed in the threads, below the bed plate, through which the shuttles or bobbins conduct second lengths of thread, whereupon the needles are further withdrawn and the threads pulled tight to form the stitches.
During the stitching operation, the presser plate is lowered onto the material assembly to hold it in place on the bed plate, whereupon the presser plate is elevated slightly to permit forward movement of the material assembly. The presser plate further limits upward movement of the assembly so that the needles may be withdrawn therefrom. The presser plate includes a similar plurality of transversely oriented holes aligned with the holes in the bed plate for passage therethrough of the needles during the stitching operaton.
Some quilting machines of the above type have used horizontally reciprocal shuttles, as in the beforementioned Schlegel quilting machine and as more fully described in U.S. Pat. No. 1,802,869, issued Apr. 28, 1931, to Gustav A. Boettcher and U.S. Pat. No. 3,253,558, issued May 31, 1966, to Fritz Hagen, while other quilting machines have used rotary bobbins of a type described in U.S. Pat. No. 1,221,857, issued Apr. 10, 1917, to August Hildt. The principal advantage which results from the use of a rotary bobbin is that the needles may be driven continuously, between upper and lower positions, with no delay or dwell time or other irregularities in the movement. Such needle movement is quieter and faster and minimizes the stresses on the needle mechanism so as to minimize machine downtime and increase the life of all parts.
On the other hand, there are a variety of overriding disadavantages that attach to quilting machines using rotary bobbins and, as a result, they are used very infrequently. For example, in order to provide a bobbin having enough thread capacity to eliminate the necessity for frequently stopping the machine to replace a bobbin, an amount of room would have to be provided for each bobbin which is simply unavailable in modern quilting machines having a large number of closely-spaced needles. Other problems result from the complexity of the necessary drive system for a multiple bobbin arrangement.
These disadvantages of a rotary bobbin do not exist with horizontally reciprocal shuttles. In a shuttle system, a series of parallel races are provided immediately below the bed plate and one, two, or more shuttles may be positioned in longitudinally-spaced relationship in each raceway. The multiple shuttles are driven back and forth by a shuttle stick which is supported with all other shuttle sticks so that all shuttle sticks and all shuttles are driven simultaneously. The needles are positioned so that the loops in the threads are formed in the raceways and the shuttles pass therethrough, creating a continuous lock stitch of the type shown in Federal Standard No. 751a Stitch Type 301.
In a conventional quilting machine of the type including plural, horizontally reciprocal shuttles, the needles are typically mounted on a needle support bar which is connected via a connecting rod and a lever to an oscillatory shaft. The oscillatory shaft is generally driven from the main drive shaft by means of an eccentric mounted on the main drive shaft, an eccentric ring mounted on the eccentric, and a connecting rod which connects the eccentric ring to a lever on the oscillatory shaft. Thus, rotation of the main drive shaft and the eccentric causes oscillation of the lever and the oscillatory shaft. The take-up mechanism, which may be a whip bar, butterfly, or the like, is mounted on a shaft which is either physically connected to the needle bar for movement therewith or which is connected to the oscillatory shaft by a connecting rod and a pair of levers so as to rock therewith.
A number of problems result from a mechanism of the type just described. Since the take-up mechanism is either directly connected to the needle bar or is directly driven by the needle bar drive shaft, both operate in timed sequence. Thus, as the needles begin to move downwardly, so does the take-up mechanism, providing slack in the threads at this time. Ocassionally, this slack causes one of the threads to loop under its associated needle and the needle snaps the thread as it moves downwardly into the material assembly. Each time this occurs, the machine must be stopped so that the thread can be rethreaded into the needle. Furthermore, until the broken thread is noticed, an irregularity occurs in the sewing pattern and this must be corrected at a subsequent time, typically by hand. This thread breakage is a substantial problem because it not only decreases machine efficiency but increases the labor required to quilt a given length of material.
It is not until the needles have reached the bottom of their strokes and started to move upwardly that loops are formed in the threads, beneath the material, for the shuttles to pass through. In a conventional machine, where the take-up mechanism operates synchronously with the needle bar drive, if the needles moved continuously, when they started to move upwardly, so would the take-up mechanism, preventing the formation of loops and the proper operation of the shuttles. To prevent this from happening, a variety of techniques have been developed for placing the needles "in neutral" as soon as the loops are formed to provide an opportunity for the shuttles to pass therethrough. In a mechanism of the type described previously, the most common technique for placing the needles in neutral is to cause the lever, which is positioned between the oscillatory shaft and the needle bar connecting rod, to pass beyond the point where the connecting rod and the lever are in line. Thus, considering, by way of example, one hand of a clock, the lever moves from some starting position, say 2:00 o'clock to 7:30, in a clockwise direction, and then back again, where the needles are in their lower position when the lever is at 6:00. When the needles start moving downwardly, with the lever at 2:00 o'clock, so does the take-up mechanism. When the lever reaches 6:00 o'clock, the shuttles begin to move forwardly. As the lever moves from 6:00 o'clock to 7:30, moving the needles upwardly, loops are formed for the shuttles to go through and the shuttles enter such loops. As the lever moves from 7:30 back to 6:00, the needles again move downwardly and the thread take-up mechanism begins to draw the thread in. However, since the needles are moving downwardly, the loops are maintained for continued passage of the shuttles therethrough. Finally, when the lever reaches 6:00 o'clock and starts moving back towards 2:00, the needles move upwardly with the take-up mechanism but, by now, the shuttles have passed sufficiently through the loops to insure stitch formation.
This hump in the needle stroke, or some equivalent mechanism, has been required in all prior quilting machines of the type including horizontally reciprocal shuttles. For a further discussion of this operation, reference should be had to U.S. Pat. No. 507,757, issued Oct. 31, 1893, to Louis Schultz, the beforementioned Schlegel U.S. Pat. No. 3,385,246, and British Patent No. 1,188,377.
A number of additional disadvantages result from this hump or delay in the needle stroke. The irregular movement of the needles and the oscillatory drive shaft required therefor contribute to the overall high noise level of the machine, which creates an uncomfortable working environment for the machine operator. The oscillatory movement of the needles and take-up drives creates vibrations which both limit the operating speed of the machine and increase the stress on the parts. As a result, most conventional quilting machines are highly inefficient, operate substantially less than 50% of the time, and must be overhauled frequently. Because of the number of variables that need to be monitored, a relatively highly skilled operator is required who must watch the machine constantly.